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09-24-2015, 06:52 AM   #1
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K-30, old AF lens, shooting/stopdown issues

Hi forum,

I'm having issues with a particular lens on a newly-acquired K-30. The lens in question is a Promaster AF 19-35mm 3.5-4.5. It was previously working fine on a K-x. Other lenses, such as my Pentax-F 50mm 1.7, function fine in every way.

When I put this lens on, aperture ring set to "A", it will shoot one image successfully, with working autofocus. After that it makes a "flip" noise as it would taking a stop-down reading, and then stops working correctly. In this condition the following are true:

1. The viewfinder is about 50% dim and out of focus
2. The autofocus is unable to find anything

If I switch to "Manual" mode and try to take a green-button reading, it makes "half" of the flipping sound that it normally does with another lens. The stopping down does not appear to affect the exposure-- taking a reading at f3.5 and f22 produce the same shutter time. taking a picture with the same metering at f3.5 and f22 produce images at the same exposure.

Also, when this is happening, turning the camera to "off" does not turn the camera off. It will stay on trying to shoot, and intermittently making fluttering stop-down noise, until MAYBE it turns off by itself 10 seconds later.

Any ideas? Is this lens just junk?

09-24-2015, 07:40 AM   #2
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First: Turn the camera around and look at the lens - is the aperture stuck stopped down when this happens?

Second: Check the lens off the camera - if you flip the aperture control lever on the lens with you finger do the blades stop down smoothly and quickly and then open back up swiftly or do they get stuck? Check the contacts on the lens and the camera and clean them off in case of some shorting that might confuse the camera during operations.

Last: Have you tried using it with the Aperture ring on a specific f/stop and using Manual mode with green button like you would an M or K series lens? If you do, then see if when you press the green button the lens stops down and reopens.
09-24-2015, 09:04 AM   #3
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Is the mount painted?

I've found that Pentax Bodies dont like mounts that are non conductive. Many old pieces of glass have black paint on the mount. If it is painted, the situation can be remedied with a bit of emery cloth to removed the paint.
09-24-2015, 10:21 AM   #4
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QuoteOriginally posted by mattt Quote
Is the mount painted?

I've found that Pentax Bodies dont like mounts that are non conductive. Many old pieces of glass have black paint on the mount. If it is painted, the situation can be remedied with a bit of emery cloth to removed the paint.
Sounds like your lens might be the Tokina 19-35mm autofocus, rebadged for Promaster. No painted surfaces, and it should operate just fine.

Have to say, it's possible you may have the beginnings of the sticky aperture control problem that has plagued quite a few K30s & K50s. It seems to first show on a particular lens, and then starts generalizing to others as the mechanism deteriorates. From what I've read, the fix is to have the mirror box assembly replaced.

Hope this worst case scenario is not your problem, but it has become a common issue.

09-24-2015, 10:30 AM - 1 Like   #5
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QuoteOriginally posted by sivadbop Quote
1. The viewfinder is about 50% dim and out of focus
2. The autofocus is unable to find anything
QuoteOriginally posted by sivadbop Quote
Any ideas? Is this lens just junk?
Are you sure it is the lens? I know you have not had problems with other lenses, but the symptoms sound a lot like the aperture actuator/mirror controller issues that have been reported for the K-30/K-50 cameras.

1) With lens off the camera, flick the aperture actuator to confirm that it moves freely with no friction through its full range of motion. Also confirm that it opens fully on full deflection.

2) As noted above, visually confirm that the aperture is wide open for focusing. Similarly, confirm that the stop-down mechanism functions properly through the exposure cycle...use a 5 second exposure to make the task easier.

If #1 fails, it is the lens. If #2, it is probably the body. If both are OK, it may still be the mirror controller. The failure of the AF and blurry viewfinder are both indicators of this condition. (The AF system depends on accurate positioning of the main mirror.) Is it safe to assume that AF and manual focus in live view still work?


Steve
09-24-2015, 01:57 PM   #6
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QuoteOriginally posted by stevebrot Quote
Are you sure it is the lens? I know you have not had problems with other lenses, but the symptoms sound a lot like the aperture actuator/mirror controller issues that have been reported for the K-30/K-50 cameras.
As someone who had the Aperture Control Block fail on a K-50 - I can say it didn't manifest like this at all. It did focus fine and worked well from that perspective. It failed to stop down as much as it was set to do so my shots came out underexposed. The problem was crazy and random to a degree. Nothing says it can't manifest in this way but most of the people I know of never saw problems during viewfinder operations.
09-24-2015, 02:30 PM   #7
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QuoteOriginally posted by UncleVanya Quote
As someone who had the Aperture Control Block fail on a K-50 - I can say it didn't manifest like this at all. It did focus fine and worked well from that perspective. It failed to stop down as much as it was set to do so my shots came out underexposed. The problem was crazy and random to a degree. Nothing says it can't manifest in this way but most of the people I know of never saw problems during viewfinder operations.
I would like to second that. It is strange that the camera doesn't switch off. It would suggest some sort of short of the pins in the mount, which could also then affect the operation of the aperture lever, cause a mirror flop etc. etc.
09-24-2015, 04:15 PM   #8
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QuoteOriginally posted by UncleVanya Quote
As someone who had the Aperture Control Block fail on a K-50...
As someone who had the mirror controller fail on a K-50, I can affirm that the symptoms* are very characteristic of that problem. FWIW, the two mechanisms share a common set of electronics and the issues are likely related. Some cameras have had both replaced and some only one or the other. That is why I called termed it "aperture/mirror". By symptom, the aperture block failure is the more common problem, but the mirror issue is not far behind.


Steve

* Dim viewfinder, PDAF fails, manual focus impossible (fuzzy), erratic viewfinder metering. What is not present is a general failure of the aperture and focus mechanism...live view works fine in all regards.


Last edited by stevebrot; 09-24-2015 at 04:22 PM.
09-24-2015, 06:32 PM   #9
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QuoteOriginally posted by stevebrot Quote
As someone who had the mirror controller fail on a K-50, I can affirm that the symptoms* are very characteristic of that problem. FWIW, the two mechanisms share a common set of electronics and the issues are likely related. Some cameras have had both replaced and some only one or the other. That is why I called termed it "aperture/mirror". By symptom, the aperture block failure is the more common problem, but the mirror issue is not far behind.


Steve

* Dim viewfinder, PDAF fails, manual focus impossible (fuzzy), erratic viewfinder metering. What is not present is a general failure of the aperture and focus mechanism...live view works fine in all regards.
That is interesting. The Precision repair receipt only mentioned "Aperture Control Block" so I don't know if the mirror parts were involved in the repair or not on mine. I assume from what you are saying that they are common parts? In none of the previous threads I have seen did I see this set of symptoms but I don't read every thread so I may have missed it.
09-24-2015, 07:17 PM   #10
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QuoteOriginally posted by UncleVanya Quote
I assume from what you are saying that they are common parts?
My understanding is that the shutter, mirror, and aperture control is integrated on a single component. I am not sure about the mechanical parts.


Steve
09-24-2015, 08:07 PM   #11
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I'd say definitely aperture control block problem.
Cf. this thread.
09-24-2015, 08:24 PM   #12
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THANK YOU all so much for your feedback... I will try to respond clearly.


1. Is the aperture stuck stopped down in this malfunctioning state? Generally no, but sometimes breifly. Eventually, and somewhat unpredictably, it opens wide and stays that way.

2. Does the aperture control lever work on the lens (detached from body)? Yes, smoothly.

3. Contacts on lens? Scrubbed with a microfiber cloth with isopropyl alcohol...

4. Use with aperture ring on a specific f/stop w/ green button... does lens stop down and reopen? No... aperture stays wide open while shutter fires/mirror flips despite the aperture ring setting.

5. Is the mount painted? No, it's the Tokina /Vivitar plastic-fantastic with a metal mount.

6. Flick the aperture actuator with lens demounted... flicks fine, quick and smooth

7. How does stop-down mechanism function through the exposure cycle? On this 19-35 lens? It does not function. In manual mode... If I set the exposure time to 2sec, and manually cycle the aperture from 3.5 to 29, I fire the shutter and it exposes with the aperture wide open every time. No tight apertures.


It's again worth noting that 2 other AF lenses, a sigma 28-70, and the Pentax-F 50, work perfectly.

The mounting of this lens is causing these mirror misfires, and strange electronic behavior--- specifically, the menus not changing as I cycle the wheel, and the camera staying on until the shuttter is fired, after I have switched it to "off".
09-24-2015, 08:56 PM   #13
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QuoteOriginally posted by sivadbop Quote
THANK YOU all so much for your feedback... I will try to respond clearly.


1. Is the aperture stuck stopped down in this malfunctioning state? Generally no, but sometimes breifly. Eventually, and somewhat unpredictably, it opens wide and stays that way.

2. Does the aperture control lever work on the lens (detached from body)? Yes, smoothly.

3. Contacts on lens? Scrubbed with a microfiber cloth with isopropyl alcohol...

4. Use with aperture ring on a specific f/stop w/ green button... does lens stop down and reopen? No... aperture stays wide open while shutter fires/mirror flips despite the aperture ring setting.

5. Is the mount painted? No, it's the Tokina /Vivitar plastic-fantastic with a metal mount.

6. Flick the aperture actuator with lens demounted... flicks fine, quick and smooth

7. How does stop-down mechanism function through the exposure cycle? On this 19-35 lens? It does not function. In manual mode... If I set the exposure time to 2sec, and manually cycle the aperture from 3.5 to 29, I fire the shutter and it exposes with the aperture wide open every time. No tight apertures.


It's again worth noting that 2 other AF lenses, a sigma 28-70, and the Pentax-F 50, work perfectly.

The mounting of this lens is causing these mirror misfires, and strange electronic behavior--- specifically, the menus not changing as I cycle the wheel, and the camera staying on until the shuttter is fired, after I have switched it to "off".
I wonder if this 19-35 could have more resistance than the other two lenses. I would be worried if it puts more strain on the aperture lever in the camera and physically prevents it from moving. If I were you I would probably try not to mount that 19-35 until you figure out what's going on :P.

Is there by any chance any sign of oil on the aperture when you close it down by hand?
09-25-2015, 01:28 AM   #14
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To some extent I will reiterate what I said in post #4, based what I've read multiple times about this problem with the K30/K50.

It often starts occurring with only one lens, and then begins to generalize to others.

Pop the 19-35mm back on your KX, and I'm guessing it will work fine. The lens apparently has some particular wrinkle to it that is allowing the K30 problem to show it's self. As the faulty K30 parts continue to deteriorate, it will then generalizes to other lenses.

I feel fairly certain of this, as a few weeks ago I began reading all I could on the subject of K30/K50 failures. I'd been contemplating the purchase of a K50, but this information steered me away from it. Instead, I located a mint K200d to go along with my slightly roughed up example (bought new in '09).

Btw, I've owned the 19-35mm Tokina going back to film days, and it's a great lens. Hang on to your Promaster version, as it will be real winner on the Pentax full-frame camera (should you choose to someday go there!).
10-03-2015, 08:14 AM   #15
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SOLVED (update from OP):

It was the lens.

At the end of my wits, and not feeling right about sending the K-30 back to the earnest seller on eBay, I disassembled the lens.

I found the internal flat metal ring that guided the aperture stop. It looked a little bendy, so I grabbed the little tab that sticks out as the diaphragm release with pliers and flattened the ring against my work surface. Put it all back together, and it works 100%.

This is a dumb mechanical problem I should have ruled out earlier--essentially a bent diaphragm lever--but hey, I know a little more about the lens.

Thanks for your analyses. This was totally making the camera sh*t its pants electronically when the aperture didn't physically spring back open after stopping down-- but I guess I can't hold that against the software.

Last edited by sivadbop; 10-26-2015 at 07:09 PM.
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